The invention relates generally to the field of magnetization and, more particularly, to substrates having cavities which contain a magnetized compound.
Advances in micro-systems technology have spawned the rapid development of a variety of devices for both research and commercial use. These devices include accelerometers, light modulators, micro-fluidic devices, micro-motors, molecular filters and various actuators and sensors. To date, the majority of MEMS actuators have been electro-statically driven. There are at least two reasons for this. First, electrostatic activation is compatible with standard microelectronic fabrication methods. Secondly, the electrostatic force scales relatively well at the micro-domain. Specifically, if the electric field is kept constant, the electrostatic force scales as L2, where L is the characteristic dimension of the device. Thus, if the size of the device is decreased by ten, the electrostatic force decreases by a factor of one hundred.
The implementation of magnetically actuated MEMS devices is much less developed then the electrostatic case. One reason for this is that the magnetic force for current driven devices scales as L4 when the current density is kept constant. This is two orders of magnitude weaker than the electrostatic case. This disadvantage can be overcome if permanent magnets are used. Specifically, if all the linear dimensions of a permanent magnet are reduced, the field strength at all the re-scaled observation points remains constant (assuming that the magnetization is constant). Moreover, there is no power consumption. However, few if any methods exist for producing integrated permanent magnet structures for use in MEMS devices.
Therefore, a need exists for a practical method for fabricating permanent magnet structures on the order of 10 to 100s of microns on a substrate for use as a field source in a MEMS device. More specifically, there exists a need for such a method that can be adapted for the batch processing in which tens to hundreds of devices can be simultaneous fabricated on a single silicon wafer.
A method for fabricating a permanent magnetic structure in a substrate, the method comprises the steps of: (a) providing a substrate with at least one cavity; (b) providing magnetic particles dispersed with a bonding material for forming a bonding compound; (d) filling the cavities with the bonding compound; and (e) curing the compound to form the permanent magnetic structure in the substrate.